1. Field of the Invention
The present invention relates to a toll receiving system of a toll road, and more particularly to a method which is able to read information correctly even from tickets an which information has been written at different recording density.
The present invention relates further to a magnetic record conversion method which is capable of increasing a magnetic recording capacity of a magnetic card type ticket even when an existing magnetic card type terminal equipment coexists with new equipment.
2. Description of the Related Art
In a long-distance toll road and the like dotted with entrance gates and exit gates at a plurality of locations, a toll is collected which depends on the distance driven and the type of vehicle. Specifically, a ticket in which the entrance gate information such as the type of a car, the date and hour of use or the entrance gate name is recorded magnetically in addition to printing is issued and handed over to a user at the entrance gate of a toll road, and an operator takes the ticket from the user and reads information recorded magnetically in the ticket so as to collect the toll for the use at the exit gate.
For this purpose, terminal equipment for processing tickets or cards such as a "Highway Card" which is a prepaid card and a credit card called a "Separately Paid Plate" are installed at the entrance gates and the exit gates of above-described toll road and the like.
FIG. 9 shows an example of a magnetic card type ticket MC. In FIG. 9, MS denotes a magnetic stripe, where magnetic recording is made with one side track. In an existing terminal equipment, the recording density is at 100 bits per inch (BPI), and the recording system is an FM system. Further, in the terminal equipment at the entrance gate, one track is divided into three areas MS1, MS2 and MS3 in a length direction of the track for backing up recorded contents, so that the same entrance gate information is recorded in each area. Further, in the terminal equipment at the exit gate, after the entrance gate information has been read, the exit gate information such as the toll, the exit gate name and the date and hour is recorded by overwriting in one of those areas in addition to this entrance gate information, and furthermore, the recorded information is read so as to confirm whether recording has been made correctly or not.
Recently, a trend has developed in which the quantity of information recorded at the exit gate, in particular, is increasing has developed due to such reasons that toll collection with a credit card is anticipated in the future. As a result, the storage of capacity with an existing recording system using only one track and having a capacity of 100 BPI will not be able to accommodate storage information in the new system.
Thus, it has become necessary to plan increase an in the recording capacity, but it is not practical to replace the terminal equipment at all the gates of a certain toll road with new equipment each having a larger recording capacity at the same time because the road must be closed even if temporarily. Accordingly, the terminal existing is to be gradually replaced with new equipment. In this case, however, tickets having different recording density with existing magnetic card type terminal equipment (hereinafter referred to as existing equipment) and new equipment will coexist. Accordingly, a method which is able to demodulate magnetically recorded information correctly from tickets of different recording densities is required.
Furthermore, in a conventional magnetic card system, a frequency modulation (FM) system is adopted as a coding system for digital magnetic recording.
FIG. 16 shows an example of a record by an FM system. As illustrated in FIG. 16, an FM system forms an FM code array 402 so as to perform magnetization inversion at boundaries 401A of all the bit cells in a data bit array 400 and at centers 401B of bit cells of respective data bits "1". Thus, since it is possible to obtain synchronization among bits in the unit of bit with a magnetization inversion signal 404A at the bit cell boundary when reading, high self-synchronizing capacity can be achieved. In FIG. 16, a reference numeral 403 denotes a regenerative signal, 404 denotes a detection pulse, 405 denotes a detection clock, 406 denotes a decoder input, 407 denotes decoded data, Tb denotes a bit period, and Tw denotes detection window width.
In the FM system, however, the density ratio (DR) of the maximum bit per inch (BPI) to the maximum flux reversals per inch (FRPI) determined by the characteristics of a magnetic card and a magnetic head is as low as DR=BPI/FRPI=0.5. Hence the FM system is not suitable for high-density magnetic recording.
Further, in a conventional magnetic card system, the width of the detection clock 405 at the read time, viz., the detection window width (Tw) is fixed for every system. Therefore, only a magnetic card having a fixed magnetic recording density can be read.